Closure for fluid pressure chamber of a hydraulic press



v 1967 K. HKSCHULTZ ETAL 3,353,388

CLOSURE FOR FLUID PRESSURE CHAMBER OF A HYDRAULIC PRESS Original Filed April 9, 1964 2 Sheets-Sheet l INVENTORS KARL H. SCHULTZ BY FRANK W. GORSKER ATTORNEYS fy lm 91W N v- 1967 K. H. SCHULTZ ETAL 3,353,383

w v-Mk7 m United States Patent Ofilice 3,353,388 Patented Nov. 21, 1967 ABSTRACT OF THE DISCLOSURE A closure for the fluid chamber in a hydraulic press. The closure is a diaphragm with an offset in the center directly above the male punch. The offset is approximately the size of the punch. A flexible plug is held in the offset which serves to change most forces which acted in shear on the diaphragm to forces acting in tension.

This application is a continuation of application Ser. No. 358,583, filed Apr. 9, 1964, and now abandoned.

The present invention relates to a hydraulic forming press and more particularly to the flexible closure for the pressure chamber thereof.

In one type of forming press, a fluid pressure chamber is closed at one end by a flexible closure. In forming a workpiece, "a workpiece blank outside the pressure cham her is pushed against the flexible closure by an advancing punch, or male die. As the male die advances, the fluid pressure in the pressure chamber, acting through the flexible closure, presses the blank around the die to form a workpiece conforming in shape to the shape of the male die.

In forming a workpiece in a press of this type, the

flexible closure is subjected to high forces from the fluid inside the chamber and to deflection and expansion by the male die. Repetitive deflection of the flexible closure under these high forces causes eventual rupture thereof, the more severe the deflection on each forming cycle, the less the number of forming cycles which can be expected before failure of the closure occurs.

It has been found that shearing forces (that is, forces which act across the material and tend to exert a tearing action thereon) contribute significantly more to the rapid failure of the closure than stretching =or elongating forces which act along the material. In the present invention, the closure is constructed so that the necessary expansion of the closure during formation of a workpiece occurs primarily along a portion of the closure to minimize the development of shearing forces. In brief, in the preferred form of the invention, the closure comprises a flexible diaphragm and a flexible plug, or disc. The diaphragm is shaped to define a pocket in the form of an external, circular recess, cr well, facing the male die in which the circular disc is received. The side, or wall, of the diaphragm which=deflnes the recess extends in the direction of movement of the male die and this portion of the diaphragm stretches during forming of the workpiece. The elongation of this wall in its preformed direction contributes signifioantly less to destructive fatigue of the diaphragm than a shearing force applied latterly to the surface of the diaphragm. Moreover, in the present invention, stretching of the diaphragm, for any given depth draw, is reduced to the extent that the flexible disc is compressed during the forming operation.

It is therefore one object of the present invention to reduce failure of the flexible closure in a hydraulic forming press. It is another object of the present invention to minimize shearing stresses during forming in the flexible closure of a hydraulic forming press. It is yet another object of the present invention to effect the expansion of the flexible closure in a hydraulic forming pres-s for forming operations primarily by elongation, or stretching, of the closure material. Other objects and advantages of the present invention should be readily apparent by reference to the following specification, considered in conjunction with the accompanying drawings forming a part thereof, and it is to be understood that any modifications may be made in the exact structural details there shown and described, within the scope of the appended claims, without departing from or exceeding the spirit of the invention.

In the drawings:

FIG. 1 is a cross-sectional view, in elevation, of a hydraulic press incorporating the present invention;

FIG. 2 is a cross-sectional view, in elevation, of the pressure chamber closure before pressure is applied to the pressure chamber; and

FIG. 3 is a view similar to FIG. 2 except that the closure is expanded during the formation of a workpiece and high pressure is present in the fluid chamber.

There is shown in FIG. 1 a forming press of the type disclosed in US. Patent 3,115,858. As shown in FIG. 1, the press has a frame 18 comprising a base 11, a head 12, and intermediate members 13 connecting the head and the base. A depending portion 14 of the head slidably receives a sleeve 15 which is shifta-ble up and down with respect to portion -14 by hydraulic motors 16. Each motor 16 consists of a cylinder 17 in the head and a piston 18 slidably received in the cylinder. The pistons 18 are connected by piston rods 19 to the sleeve 15. A closure 20 closes the lower end of the sleeve.

The base 11 supports a bed member on which Workpiece blanks 26 are placed for forming. A punch, or male die, 27 is slidably received in bed member 25. Punch 27 is connected by rod 28 to a piston 29 slidably received in cylinder 30 of the base. Piston 29 has an internal cylinder 31 which receives stationary piston 32.

A pump 35 takes fluid from sump 36 and delivers it under pressure to pressure line 37. A safety relief valve 38 connected between pressure line 37 and the sump limits the maximum pressure in line 37. When valve plunger 39 of valve 40 is shifted to the left, the cylinders 17 above pistons '18 are connected through line 41 and valve 40 to pressure line 37, and the cylinders 17 below pistons 18 are connected through line 42 and valve 40 to a return line 43 leading to sump 36. This lowers the sleeve 15 to engage closure 20 with workpiece blank 26, as shown in FIG. 2. As the sleeve 15 descends to expand the fluid pressure chamber 44 defined by head portion 14, sleeve 15, and closure 20, the valve 45 in passage 46 is held open (by means not shown). Passage 46 leads from a reservoir 47 or" fluid on head member 12. After the chamber 44 is filled with fluid from reservoir 47, valve 45 is closed.

The closure 20 for the lower end of the chamber 44 consists of a rubber diaphragm 50 and a rubber disc, or plug, 51 as shown in FIG. 2. The diaphragm is mounted in sleeve "15 in the same manner as the diaphragm in US. Patent 3,075,485. The diaphragm 50 has an upwardly extending flange 52 with a rib 53 which is gripped by a ring 54. The diaphragm is received inside a tubular casing 55 which is held inside the sleeve 15 when the arcuate clamps 56 on sleeve 15 are in the position shown. A ring 57, which is supported by bed member 25 when the sleeve 15 is down, helps support the diaphragm 50.

The diaphragm 50, has, in its lower surface, a pocket or offset 59 formed therein which is circular in crosssection and which defines a recess 60 also circular in cross-section. The disc 51 is received inside the recess 60. The offset 59 has a generally cylindrical wall, or side, 61 which has an inner face 61a (inside the pressure chamber) and an outer face 61b (in the recess outside the pressure chamber). In the relaxed condition of the diaphragm 50 (as shown in FIG. 2 which shows in cross-section the preformed, or molded, shape of the diaphragm) the inner face 61a extends vertically (in the direction of movement of punch 27) as indicated by arrow A. Preferably, however, the outer face 61b of the offset is slightly canted (sloping slightly outwardly as it extends upwardly) as shown in FIG. 2, to hold the disc 51 in the recess even when the sleeve 15 is raised up from the bed member 25.

A high pressure pump takes fluid from sump 36 and delivers it under pressure to pressure line 66. When valve member 67 of valve 68 is shifted to the left, line 66 is connected to a line 69 which leads through head member 14 into chamber 44-. As fluid is pumped through lines 66 and 69 to chamber 44, the pressure in the chamber rises until it reaches a predetermined pressure, say 5000 pounds per square inch, determined by the setting of the adjustable relief valve 70 connected between line 66 and the sump 36. As pump 65 continues to pump fluid from sump 36, and while the setting of relief valve 70 is unchanged, fluid is returned to-the sump from line 66-and the pressure in lines 66, 69, and chamber 44 is held at 5000 pounds per square inch.

Shifting valve member of valve 76 to the left serves to connect pressure line 37 to motor line 77 for the application of fluid under pressure to chamber 30 below piston 29. At this time motor line 78, which is in communication with chamber 31 in piston 29, is connected through valve 76 to a return-line 79 leading to sum-p36. The cylinder 30 above piston 29 is continuously in communication with the sump. Under these pressure conditions, the punch 27 rises, forcing the workpiece into the closure 20, as shown in FIG. 3. During the forming cycle, if desirtable, the pressure in chamber 44 can be continuously, or intermittently, changed by adjustment of screw 80 on valve 70. In the usual forming cycle, the pressure in chamber 44 is increased, say to 10,000 pounds per square inch, and, to accomplish this, screw 80 is adjusted to shift spool 81 to the left, thereby increasing the force required to open the passage between line 66 and sump 36. The high fluid pressure forces within the chamber 44 acting on the diaphragm 50 are indicated by arrows B in FIG. 3.

As the punch 27 first starts to ascend, the diaphragm 50 creeps within casing 55 until the shoulder 54a-of ring 54 engages the top edge of the casing. Also, as the punch 27 ascends, the disc 51 is compressed. However, despite the creeping of the diaphragm and compression of the disc, the diaphragm must expand to accommodate the rising punch.

The oifse't '59 and disc 51 are in registration with the punch. It is important that diaphragm 50 and disc, or plug, 51 be separate, unconnected, members so that relative movement can occur between the wall 51a of the disc and the outer wall 61b of the offset 59 in the diaphragm. Thus the substantially vertical wall 61 of the offset elongates while the disc compresses. It has been found that, with this construction, the major portion of expansion of the diaphragm occurs in elongation of the vertically extending wall. Elongation of the diaphragm along the length of the wall 61 is significantly less conducive to fatigue of the closure material than, for example, de-

formation occurring latterly to the surface of the diaphragm material.

What is claimed is:

1. In a hydraulic press having a fluid pressure chamber and having a male die in registration with the chamber, the combination comprising a flexible diaphragm received across one end of the chamber and in front of the male die, said diaphragm having a central portion offset into the chamber and defining a recess in the diaphragm, said recess facing the male die and having an inner wall in alignment with the side wall of the male die, and a flexible plug received in said recess.

2. In a hydraulic press for forming a workpiece blank, said press having a fluid pressure chamber and having a movable male die in registration with the chamber, the combination comprising a flexible diaphragm received in the chamber to close one end thereof, said diaphragm having a central offset portion extending into the chamber with a side wall extending in the direction of movement of the die, said offset portion in registration with the male die and the side wall of the offset portion in alignment with the side wall of the male die, said offset portion defining a recess in the outer side of the diaphragm facing the male die, a flexible plug received in said recess to fill the recess, and means to advance said male die to press a workpiece blank against said plug for formation of a workpiece around said male die.

3. An apparatus dior closing one end of a fluid forming pressure chamber in a hydraulic press having a male die, said pressure chamber utilized to form a workpiece around the male die, the apparatus comprising:

(a) a flexible diaphragm having a central portion offset into the chamber and defining a recess in the chamber, said recess facing the male die, and

(b) a flexible plug received in said recess.

4. An apparatus as claimed in claim 3 wherein said recess is approximately the size of the male die.

5. In a hydraulic press for forming a workpiece blank, said press having a fluid forming pressure chamber and a movable male die in registration with the chamber, the combination Comprising:

(a) a flexible diaphragm having a central portion offset into the chamber and defining a recess in the chamber, said recess facing the male die and having a side wall extending in the direction of movement of the die,

(b) a flexible plug received in said recess, and

(c) means to advance said male die to press a workpiece blank against said plug for formation of a workpiece around said male die.

References Cited UNITED STATES PATENTS 2,696,184 12/ 1954 Dem-arest 7265 2,741,205 4/1956 Daulton 7263' 2,861,531 11/1958 Moller 72-6-3 2,966,872 1/ 1961 Schmocker 7263 3,033,143 5/ 1962 Granlrowski 7263 RICHARD J. HERBST, Primary Examiner. 

1. IN A HYDRAULIC PRESS HAVING A FLUID PRESSURE CHAMBER AND HAVING A MALE DIE IN REGISTRATION WITH THE CHAMBER, THE COMBINATION COMPRISING A FLEXIBLE DIAPHRAGM RECEIVED ACROSS ONE END OF THE CHAMBER AND IN FRONT OF THE MALE DIE, SAID DIAPHRAGM HAVING A CENTRAL PORTION OFFSET INTO THE CHAMBER AND DEFINING A RECESS IN THE DIAPHRAGM, SAID RECESS FACING THE MALE DIE AND HAVING AN INNER WALL IN ALIGNMENT WITH THE SIDE OF THE MALE, DIE, AND A FLEXIBLE PLUG RECEIVED IN SAID RECESS. 